This invention relates to a rotary engine designed to increase the rotation force of a rotor.
A conventional rotary engine as shown in FIG. 1 comprises a rotor housing 10 having a trochoidally curved inner surface and a rotor 11 having three apexes 12 and adapted to be rotated in an eccentric fashion. A seal piece 13 is mounted on each apex of the rotor to define three combustion chambers 14, 15 and 16 between the outer wall of the rotor and the inner wall of the rotor housing 10. The rotor housing 10 includes a suction port 17 for introducing an air-fuel mixed gas into the combustion chamber 14 at the suction cycle, an ignition plug 18 for igniting the mixed gas at the compression cycle and an exhaust port 19 for sending the combustion gas to the outer atmosphere. Within the rotor is provided an internal gear (not shown) which is in mesh with an external gear (not shown) provided on an eccentric shaft 20. At the start of the rotor, the shaft 20 is rotated by a self-start motor (not shown).
In the known rotary engine, the rotation of the shaft causes its external gear to be engaged with an internal gear of the rotor to permit the rotor 11 to be rotated in an eccentric fashion. By so doing, a mixed gas is introduced through the suction port 17 into the combustion chamber 14 and the mixed gas is compressed in the combustion chamber 15 and ignited by an ignition plug 18.
In the prior art rotary engine described, the explosion force (F=f.sub.A +f.sub.B), i.e., the force generated by the expansion of the exploded gas, acts on one side of the rotor and a resultant force P.sub.g is obtained. In the drawing, the arrows f.sub.A and f.sub.B denote the directions in which portions of said one side of the rotor receive the explosion force. Since at this time the center of the rotor t is displaced off the center of the shaft s the resultant force is resolved into a tangent force Pt and a centripetal force Pu, i.e., a force tending to push the center of the shaft s. The centripetal force Pu is received on the bearing portion of the shaft and the tangent force Pt, i.e. a force tending to rotate the shaft, becomes an actual rotation force. Thus, the rotation torque of the rotary engine Md is: EQU Md = Pt .times. e
where e is an amount of eccentricity between the center of the rotor t, and the center of the shaft s.
That is, if the greater resultant force Pg is obtained, a greater tangent force Pt and greater centripetal force Pu results. Thus, a greater rotation torque Md is obtained. In order to produce a greater rotation torque Md, therefore, it is necessary to make greater the combustion chamber of the rotor and the amount of eccentric force.
At the combustion cycle, therefore, an explosion force F is applied to the corresponding outer wall of the rotor and can be resolved into an explosion force fA on the advancing angle side and explosion force fB on the astern side, viewed with respect to an extension line passing through the center of the rotor t and the center of the shaft s. In this case, the explosion force fA on the advancing angle side turns into an effective rotation force and the explosion force fB becomes a reverse rotation force. Therefore, when the resultant point coincides with the center of the rotor 11, if the amount of eccentricity e is zero, no rotation force is obtained. As the amount of eccentricity e is increased, EQU fA + fB = F or Pg.
The resultant force Pg is resolved into a tangent force Pt and component force Pu and the rotation torque Md is: EQU Md = Pt .times. e
That is, no rotation force results unless an amount of eccentricity is obtained. As a result, the rotation efficiency is lowered by that extent.